Hollow Fibers Structured Packings in Olefin/Paraffin Distillation: Apparatus Scale-Up and Long-Term Stability

Following the conceptual demonstration of high separation efficiency and column capacity obtained in olefin/paraffin distillation using hollow fiber structured packings (HFSPs) in a bench scale (J. Membr. Sci. 2006, 2007, and 2010), we scaled-up this process with a 10-fold increase in the internal flow rate and a 3-fold increase in the module length. We confirmed that the HFSPs technology gives high separation efficiency and column capacity in iso-/n-butane distillation for 18 months. We systematically investigated the effects of packing density, concentration of light component, reflux ratio, and module age on the separation efficiency and operating stability. Comprehensive characterizations using scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) were carried out to probe the changes in the morphological, thermal, and mechanical properties of polypropylene (PP) hollow fibers over the aging process. The results suggest that after a long-term exposure to light hydrocarbon environments at <= 70 degrees C the morphological and mechanical properties of the PP polymer do not degrade significantly in a propane/propylene and iso-/n-butane environment.